1. Field of the Invention
This invention relates generally to laser radar systems and more particularly to a time modulated doublet coherent laser radar system.
2. Description of Related Art
Radar systems utilizing doublet RF pulse waveforms are generally known, being used, for example, in Doppler radar applications. Moreover, pulse pairs having constant time separation between the transmitted pulses and polypulse transmit formats have been utilized in radar systems for meteorological systems where weather echoes are probed for radio velocity and spectral width. Doublet pulse applications at optical wavelengths have not been used until recently because the frequency and phase of the transmitted waveform typically varies from one doublet pulse pair to the next, i.e., doublets are coherent from pulse to pulse but not doublet to doublet. However, this problem has recently been overcome, for example, by the generation and inclusion of a monitor pulse which comprises a portion of each pulse of the doublet pair transmitted and is then used as a reference during signal processing to remove the effects of fluctuations in frequency and phase of the transmitted pulse waveforms to provide measurements of range and velocity. Such a system is disclosed, for example, in U.S. Pat. No. 5,815,250, Doublet Pulse Coherent Laser Radar For Precision Range and Velocity Measurements, Thomson et al., Sep. 29, 1998.